1. Field of the Invention
This invention relates broadly to underground mining machines, and more particularly to remote control systems for underground mining machines. The invention may be used in an underground continuous miner as described herein, or used in other mining machines such as conveyor-bolters and the like.
In underground coal mining facilities, for example, there has been a long need to increase coal production, mining efficiency and operating safety procedures. One way to increase coal production and mining efficiency with continuous miners in both new and existing coal mines is to permit the continuous miner to take deeper cuts before moving to a new mining site. This practice, however, subjects the human operator of conventional continuous miners and conveyor-bolters to undue hazards rather than increasing operating safety procedures.
It has been suggested that one way to achieve increased coal production, mining efficiency and operating safety is to make the deeper cuts with continuous miners and/or conveyor-bolters operating under control of a remote control system. However, those mining machine manufacturers that may build mining machines with a remote control system do so to provide a service-reliable package that will withstand the severest electrical hazard and other mining environmental conditions, but at the expense of operating flexibility.
For example, one prior art remote control system may include basic features of an on/off control in the electrical and solenoid controlled hydraulic systems. Another may offer complex stepwise control of certain functions, but this is not a true proportional control system. Such basic and stepwise control systems are listed by the U.S. Dept. of Labor, Mine Safety and Health Administration (MSHA), as "permissible". That is, electrical and/or control systems which operate at energy levels sufficient to ignite a methane and air mixture are permitted in mines if contained in heavy metallic explosion-proof enclosures and/or other means to safely handle electrical hazards sometimes present in mines in the form of an explosive mixture of methane gas and air.
Other deficiencies in the prior art mining machine remote control system, in addition to that of lacking true proportional control features, include the absence of MSHA listed "intrinsically safe" electro-control valves and controllers for both proportional and on/off fluid control functions. That is, electrical control systems which operate at low energy levels are considered "intrinsically safe" and permitted in mines in nonexplosion-proof enclosures if the electrical energy released by the control circuit is not sufficient to ignite an explosive mixture of methane and air. This classification is in contrast to MSHA "permissible" defined above and if attainable permits much simpler control housing and wiring requirements, in addition to reducing maintenance programs and personnel requirements as compared to "permissible" systems.
Additional deficiencies in the prior art mining machine remote control systems are attributable to their lack of applicability to all coal mining machines; their inability to be retrofitted into existing mining machines; their lack of offering a light-weight control console; their susceptibility to control valve contamination and subsequent malfunction; and/or their inability to be easily repaired underground.